1. Field of the Invention
The invention relates generally to timer devices, and more particularly, to an underwater electromechanical timer that can be timely programmed to activate an external device connected to the underwater electromechanical timer.
2. Description of the Related Art
Timer devices are well known to provide delayed activation of various types of devices. Conventionally, the structure and mechanism of timer devices are specifically in accordance with its conditions of use. The following description particularly refers to an example of underwater timer.
In navigation, maritime ships happen to ground between submerged reefs, putting the ships in difficulty. In those situations, explosives are conventionally used to remove the submerged reefs. The explosives are adequately disposed on the site of submerged reefs, and underwater timers are typically connected to the explosives to trigger timely-programmed explosions.
FIG. 1 is a cross-sectional view that depicts a conventional underwater timer known in the art. The conventional underwater timer 10 comprises a casing 15 in which the slide of a control bar 17 enables to timely turn a switch 18. The control bar 17 is tightly mounted with a collar pad 12 that lies on a salt dissolvable supporting block 14 to support and keep the control bar 17 away from the switch 18. To activate the timer 10, the latch 13 that locks the control bar 17 within the casing 15 is first removed. The underwater timer 10 then is put into water. Salt dissolvable supporting block 14 contacting with water then progressively dissolves in water, which causes a progressive slide of the control bar 17 to contact with the switch 18. A rubber membrane 16 is conventionally arranged within the casing 15 to isolate the switch 18 from water contact.
The above conventional timer 10 using a salt element has several deficiencies. The dissolution of the salt element in water is difficult to control with respect to time programming purposes because multiple factors may influence the dissolution velocity. For example, under substantially high water pressure, the salt element may crack into several pieces, which increases the contact area of the salt element with water and consequently accelerates its dissolution in water. The salt element may also easily crack into smaller pieces when the timer is transported. Besides, the waterproof rubber membrane 16 may be damaged due to high water pressure, which restrains the use of the timer to limited water depths. A more reliable, robust, and precise underwater timer is thus needed.
An aspect of the invention is therefore to provide an underwater electromechanical timer that can be precisely programmed, and provides a precise activation of the devices connected to the timer without being affected by external water pressure.
Another aspect of the invention is to provide an underwater electromechanical timer that can be used in water depth levels higher than the conventional water depth levels.
Yet, another aspect of the invention is to provide an underwater electromechanical timer that is reliable and robust.
To accomplish the above and other objectives, an underwater electromechanical timer of the invention comprises the following elements installed within a casing structure. A motor-driven timer assembly mounted in the casing structure comprises a threaded member that engages an endless screw driven in rotation via a motor. Time programming of the timer is accomplished by presetting a length of sliding of the threaded member along the endless screw. The sliding threaded member causes a timely switching event of a device switch placed within the casing structure. An external device that is electrically connected to the device switch is thereby activated. To activate the timer, an activation mechanism comprised of a plunger is mounted in the casing structure. The activation mechanism is externally exposed. Under adequate external pressure exerted on the activation mechanism, the activation mechanism connects the endless screw with an output of the motor to drive the rotation of the endless screw, and causes a slide of the threaded member. The turn-on and turn-off of the motor are achieved through switches placed in the casing structure. The turn-on of the motor is effectuated by the activation mechanism once the activation mechanism has engaged the endless screw with the output of the motor. The turn-off of the motor is effectuated when the threaded member has reached the end of its sliding course. Resilient controller and protection elements are further mounted between the endless screw and the motor and between the device switch and the threaded member to prevent undesired activation events, thereby improving the reliability and robustness of the timer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.